The filter according to the present invention is suitable for a pyrotechnical gas generator, that is, a gas generator comprising a charge of pyrotechnical propergol which will create the essential gases for the inflation of the associated airbag during its combustion.
Filters for such pyrotechnical gas generators such as the one disclosed in the document U.S. Pat. No. 7,823,919B2 are known in the prior art. The disclosed filter comprises a filtering material and is located arranged between a combustion chamber and discharge nozzles of the housing of the gas generator. On the other hand, this system has in particular a first disadvantage which consists of a risk of disturbing the flow of gas passing through the discharge nozzles if the filter is expanded or dilated during the igniting of the gas generator. In fact, a wave of strong and significant pressure is generated during the functioning of the igniter which can bring about a deformation or expansion of the filter which can lead to a partial obstruction of the discharge nozzles. This can also be produced during the ignition of the pyrotechnical material contained in the combustion chamber. The gas flow is then disturbed, which can bring about a different inflation speed than the one desired and therefore lead to a variability in the operation of the gas generator, a variability which results in an oversizing in particular of the generator walls (and therefore a charge) to be able to guarantee the safety of the generator conditions of operation.
A second disadvantage consists in that the filtering material of the filter in question can bring about a variability of the ignition because a part of the hot particles and hot gases ejected by the igniter in the charge of propergol can go directly into the filtering material. In this case these hot particles and hot gases are no longer in intimate contact with the propergol, which reduces the quality of the ignition and even more increases the variability of the functioning.